440ex broken valve

[chubbz2006]

I just putin a 440 kit and already broken valve cant figure out what the problem would timing matter? also my head was just ported and polished and now it has big indentetions in the combustion chamber from the valve hitting it. does anyone know if i can resurface it or do i have to replace it? thank you much help needed

[Colby@C&DRacing]

Timing could have been the problem along with alot of other factors. You could have floated a valve or the valve could have just failed. As for reusing the head that will be determined by the location and exstent of the damage. Can you post pics?

[chubbz2006]

I dont know how to post pics on here but thanks for the response.

[sixer3]

did the valve hit the piston, if so you most likely also damaged the valve train, i.e: rocker arm. also you'll most likely have to get a new head, but a pic would help.

you just said you broke a valve. so it i wasnt sure if you floated a valve or what(most likely)

[chubbz2006]

the valve was riding on top of the piston that why it just stalled on me..i cant get a pic up but it looks pretty badly damaged around that exhaust valve and the valve seat is also pretty badly damaged. what is floating a valve exactly mean? thank for your help.

[Kaleigh]

chubbz send you pic to me and ill post it for you if you want..

patiya1215@hotmail.com

[chubbz2006]

cool i send a pic its off my phone so the quality may not be too good but you can see damage. thank you kaleigh

[Kaleigh]

OMG dude.. that just made my heart drop when i seen it..

btw.. no prob Chubbz.. anytime you need help.. :macho

[Trevor]

That dose not look good. I feel for ya !

[AtvMxRider]

look for a new head

[250X_project]

Ouch man. Yea a new head will be in order. I'm also interested in what "floating a valve" means.

[gojk]

Originally posted by 250X_project
Ouch man. Yea a new head will be in order. I'm also interested in what "floating a valve" means.

Floating a valve is basically the valve not springing back closed fast enough, usually because of using too weak of springs, and the piston hitting the valve. From the looks of the head I would say you floated a valve. If it was timing you prob would have got both exhaust valves.

[joeb23]

ouch that looks pretty bad... I have seen worse though. my friend broke all 4 valves off, you should have seen the whole in the piston.

[chubbz2006]

thanks for everyones help this really sucked i was in pismo when it happend i was just going to brake it in too. anybody have a head for sale. if not im looking into the yzf426 how diffficult is that to put in? thanks

[lpmaster]

honestly from what i can tell, that looks fixable. talk to your local machinesst about it, from what i can tell it looks like the one i bought for 20 bucks off ebay, and had it re-machined here is s.d. and its still running.

if not, and youve a lot of money, time, and access to a very good welder with spare time, you can do a hybrid build with the motor of your choice, but its a lot more work than dropping in the motor

[250X_project]

Well than I've had an X with a floated valve. I've seen a 440 with all 4 valves gone.

[lpmaster]

floating valves usually doesnt happen from weak or old valve springs. it usually happens because people try to get as much compression as possible, by elminating base gaskets, decking cylinder and/or head hieght. and using a high compression piston with a high lift cam....now sure these will increase compression9decreasing combustion chamber) but at a price, all good engines should be put together and clay checked before final assembly and running. timing can also have a role in this...theres a lot of factors to floating valves, but the ultimate is the engine builder ( putting in a piston backwards can also cause something like this i belive

[joeb23]

U might want to try and see if there are any heads on ebay, they usually arent that expensive unless its brand new...duh

[GPracer2500]

Originally posted by lpmaster
floating valves usually doesnt happen from weak or old valve springs. it usually happens because people try to get as much compression as possible, by elminating base gaskets, decking cylinder and/or head hieght. and using a high compression piston with a high lift cam....now sure these will increase compression9decreasing combustion chamber) but at a price, all good engines should be put together and clay checked before final assembly and running. timing can also have a role in this...theres a lot of factors to floating valves, but the ultimate is the engine builder ( putting in a piston backwards can also cause something like this i belive

Floating a valve IS often caused by a weak/old/broken valve spring. High RPM can also be a primary factor. Using oversized aftermarket valves or valves of a different material without upgrading to springs that are matched to the weight of the new valves can also contribute to valve float.

Valve float is specific occurance that can cause a valve to contact a piston. But there are other reasons P-V contact could happen (some of which you mentioned) that have nothing to do with valve float.

[lpmaster]

well, i had a vlave hit my piston, used the exact same valve springs in a new motor, and never had a porblem, although im no enigne builder, thats where my theory came from, i definately would not argue with you there though

[1fst400]

throw a 450r motor in there. thats what I did and I LOVE it.

[250X_project]

When I floated a valve it was because of keeper failure. I'm sure a lot of people may use high lift cams with stock springs causing this...many causes for it

I don't know what my friend did, but he got all 4 valves and mashed his head....:eek2:

[GPracer2500]

Originally posted by 250X_project
When I floated a valve it was because of keeper failure...

A keeper failing and allowing a valve to drop is not a floated valve. "Valve float" is not a generic term for anytime a valve contacts a piston.

I'll expand on what gojk posted: Valve float is when a valve spring fails to maintain normal control of a valve. As the camshaft spins around, the cam lobe (or rocker arm) is physically contacting the valve at all times when the valve is being opened--of course, right?, the cam lobe is pushing the valve open. But as the valve closes the valve spring still maintains that contact and closes the valve. The valve spring pressure keeps the valve in contact with the cam lobe (or rocker arm) at all times except when the valve is fully closed. The springs don't just snap the valve shut any old way they want--they must follow the shape of the cam lobe.

When a valve "floats" the contact between the valve and the cam is momentarily lost. If a valve spring is weak then at high RPM the spring may not be able to keep the valve pressed up against the cam lobe as the valve closes. Basically, the cam lobe accelerates away from the valve and the spring can't work fast enough to maintain contact. The valve lags behind and "floats" for a moment. This is how valve float can cause piston to valve contact.

In the 400EX, the valve springs not only have to control the mass of valve but they also have to deal with the mass of the rocker arms. The greater the mass of these parts the more inertia they have and the harder it is for the springs to keep things in control. This is part of the reason 400EX's have dual valve springs (one inside the other).

Here's a super-slow motion video of valve float taking place. This particular engine is a side valve design with pushrods (think: lawn mower engine). If you're not sure what your looking at then it's kind of hard to interpret, but when the timer in the upper right hand corner reads about 007008 the float begins. You can see a small gap develop between the valve stem and the pushrod. That's valve float.

Slow-mo valve float vid (0.7meg WMV file) (http://www.engr.colostate.edu/~dga/high_speed_video/mechanisms/MERC_valve_spring_close-up_1000vs6000rpm_3000fps.wmv)

[250X_project]

Okay thanks. That makes much better sense. I like that video, where did you find that? Thanks